XML 19 R48.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Summary of Significant Accounting Policies (Direct Premium Attributable By Segment) (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Segment Reporting Information [Line Items] |  |  |
Annual direct premiums written | $ 2,853,169 us-gaap_DirectPremiumsWritten | $ 2,737,472 us-gaap_DirectPremiumsWritten | $ 2,655,720 us-gaap_DirectPremiumsWritten
Private Passenger Automobile [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Annual direct premiums written | 2,223,073 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_PrivatePassengerAutomobileMember | 2,165,557 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_PrivatePassengerAutomobileMember | 2,140,531 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_PrivatePassengerAutomobileMember
Homeowners [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Annual direct premiums written | 374,436 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_HomeownersMember | 340,013 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_HomeownersMember | 318,295 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_HomeownersMember
Commercial Automobile [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Annual direct premiums written | 135,928 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_CommercialAutomobileMember | 104,689 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_CommercialAutomobileMember | 74,655 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_CommercialAutomobileMember
Other Lines [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Annual direct premiums written | $ 119,732 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_OtherLinesMember | $ 127,213 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_OtherLinesMember | $ 122,239 us-gaap_DirectPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = mcy_OtherLinesMember

X
- Definition Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums written. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 17 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b),(c)(1) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
Name: | us-gaap_DirectPremiumsWritten
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mcy_CommercialAutomobileMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mcy_HomeownersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mcy_OtherLinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=mcy_PrivatePassengerAutomobileMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |